Preparation of high fructose syrups from citrus residues

ABSTRACT

The sugar content of citrus press liquor is enhanced by separating citrus solids, extracting fructose, glucose, and sucrose from the solids, and recombining the aqueous extract to increase the sugar content thereof. By inversion of the sucrose present in the sugar-enhanced press liquor, a high fructose syrup can be readily obtained which is indistinguishable from high fructose corn syrup. When separation is effected by centrifugation, a biocidally active colloidal phase is formed from which citrus terpenes and limonene can be extracted, resulting in a press liquor suitable for fermentation. The solid residue remaining after extraction can also be recycled with the remaining press cake.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of copending, commonlyassigned U.S. patent application Ser. No. 06/405,037 filed Aug. 4, 1982now U.S. Pat. No. 4,488,912.

DESCRIPTION OF THE INVENTION

1. Technical Field of the Invention

This invention relates to a process for increasing sugar levels incitrus press liquor and for obtaining a concentrate containing highsugar levels from citrus press liquor. The sugar enhanced citrus pressliquor of the press invention can be concentrated and the sugar invertedto yield a commercially useful syrup having a high level of fructose.

2. Background Art

One of the problems associated with the growth an expansion of thefrozen citrus concentrate industry has been the disposal of peelresidues as well as the rag, juice sacs and seeds from citrus fruit.Various approaches to solving such problems have been summarized by J.W. Kesterson and R. J. Braddock in "By-Products and Specialty Productsof Florida Citrus", Fla. Agr. Exp. Sta. Bul. 784 (December 1976), thecontents of which are incorporated by reference herein. As used herein,the term "citrus" refers to any member of the genus Citrus, includingbut not limited to the orange, grapefruit, tangerine, tangelo, lemon,lime, citron, and mandarin. Most of the waste residue from commercialjuice extractors is shredded, limed, cured and pressed into pressliquors and press cakes which are then processed independently. Curedpress cakes are dried in a feed mill to yield "dried citrus pulp", (DCP)from which feed pellets for cattle, sheep and other ruminants areprepared. The press liquors are usually concentrated in multiple effectheat evaporators to yield citrus molasses, while d-limonene is obtainedfrom the condensate. As is known from Greathouse et al. U.S. Pat. No.3,023,144 and Gauvreau U.S. Pat. No. 3,787,566, this material hasbiocidal activity in addition to being useful as a fragrance. However,present commercial processes still discard valuable and importantcomponents from citrus fruit processing operations.

B. R. Breslau et al. describe in Trans. Citrus Eng. Conf. ASME Lakeland22: 53 (1976) a process for recovering the soluble constituents ofcitrus press liquor by screening and ultrafiltration of the resultantfiltrate with hollow fibers to separate solids and oil suspensions fromthe citrus press liquor and to produce a permeate faction containingdissolved sugars. The ultrafiltration retenate fraction containingsuspended solids (including finely divided peel, pulp, and seed residuespresent in the screened liquor) is considered waste to be used asconventional animal feed or to produce molasses.

A general object of this invention is to provide a process forseparating and recovering valuable products from finely divided solidwaste material ("shards") present in citrus press liquor.

A principal object of this invention is to provide a process forrecovering sugars from the shards present in citrus press liquor.

Another object of this invention is to provide a process for purifyingsugar extracts obtained from citrus waste material to yield mixtures ofnon-reducing sugars as well as glucose and fructose.

A more particular object of this invention is to provide a process forpreparing high fructose syrups, comparable to commercial high fructosecorn syrup sweeteners, from citrus waste materials.

Another principal object of this invention is to provide a process forrecovering limonene and other antimicrobial materials present in citruspress liquor.

A further object of this invention is to provide citrus press liquorwhich is substantially free of such antimicrobial materials, therebypermitting its use as a feedstock in microbiological processes.

Yet another object of this invention is to provide a process forrecovering the solid residues of sugar-extracted shards obtained fromcitrus press liquor for use in the production of dried citrus pulp.

Upon study of the specification, drawings and appended claims, furtherobjects, features and advantages of the present invention will becomemore fully apparent to those skilled in the art to which this inventionpertains.

DISCLOSURE OF THE INVENTION

Briefly, the above and other objects of this invention are obtained inone aspect thereof by providing a process for increasing the sugarcontent of citrus press liquor which comprises separating a majorportion of finely divided shards consisting essentially of suspendedpeel, pulp and seed citrus solids from citrus press liquor andextracting fructose, glucose, and sucrose present in the separatedsolids. The aqueous extract is preferably recombined with citrus pressliquor which is substantially free of citrus solids to increase thesugar content thereof by at least 20 percent, generally 30-40 percent byvolume.

The present invention is based in part upon the discovery that citruspress liquor, which is obtained by pressing waste citrus material suchas peels, pulp and seeds, contains at least three distinct and easilyseparable physical and chemical phases. Approximately 1-5 percent (byvolume) of the press liquor is composed of small insoluble fragments or"shards" which are not removed by existing commercial processes forseparating press cake from press liquor. In accordance with thisinvention, press liquor is treated by separation techniques such asultrafiltration or centrifugation to recover these shards. The shardsare then suspended in a hot aqueous solvent, preferably water, toproduce a sugar-enhanced aqueous extract which is recombined with thepress liquor supernatant from the initial separation treatment toincrease the sugar content thereof. The resultant sugar-enhanced citruspress liquor typically contains solubilized hemicelluloses and pectinsalong with fermentable sugars at a level over 20 percent greater thaninitially present in the press liquor starting material. Approximately95 percent of these sugars are represented by the dissaccharide sucroseand the C6 reducing monosaccharides fructose and glucose.

When the initial crude citrus press liquor is centrifuged, separation ofthe press liquor into three distinct phases occurs. The top phase is abright yellow (or green, depending on the source of the oranges)colloidal layer which generally comprises 1-5 percent of the totalvolume and contains, among other components, d- and d,l-limonene. Themiddle layer is an aqueous phase containing dissolved sugars togetherwith stabilized hemicelluloses and pectins present in the original pressliquor, and its color varies from pale yellow to pale brown depending onthe pH; generally, a lighter color reflects a lower pH. The third phaseis a solid pellet comprising the shards. The amount recovered variesfrom batch-to-batch of citrus press liquor, but is generally about 1-10g/100 ml. Alternatively, the solids can be separated from the pressliquor by ultra-filtration, e.g. as described by R. J. Braddock et al,J. Food Sci 47 (3): 946-948 (1982). Tests in our laboratories as well asin the testing laboratories of two major filtration membranemanufacturers have resulted in uneconomically low production rates asmeasured in gallons processed per square foot of membrane per day.Centrifugation is presently preferred as it readily separates the threedistinct phases for immediate subsequent treatment.

It has been found that heating these shards suspended in an aqueoussolvent for a brief period of time, preferably in a volume of solventroughly corresponding to the original volume of press liquor for 10-15minutes at 65°-85° C., then cooling, separating the shard residues andrecombining the aqueous extract with the separated press liquor lineconsistently increases the hexose content of the press liquor by atleast 20 percent, typically 30-40 percent or more on a volume basis,thereby returning a substantial amount of sugar to the press liquorline.

The solid material or shards, remaining after heating in water toseparate the additional sugar components, can be dried and processed foranimal feed if desired. Adding the extracted shard residues, consistingessentially of water-insoluble pectins, celluloses, and hemicelluloses,back to the press cake line increases the solids content thereof by atleast 10 percent, typically 15-20 percent or more on a dry weight basis.This represents a substantial additional yield of dried citrus pulp frommaterials which have otherwise been lost in the citrus molasses line.

While the aqueous solution containing glucose, fructose, and sucrose canbe independently inverted, it is more economical to return this solutionto the press liquor line for a single step inversion of the sucrosepresent in both solutions. 95 percent of the sugars present in theaqueous extract are fructose, glucose, and sucrose, the latter beingsusceptible to inversion, e.g. by treatment with invertase according totechniques well known in the art such as described in U.S. Pat. No.2,126,947, to yield a 50:50 mixture of glucose and fructose.

Inversion can take place at any point in the process subsequent toenhancement of the sugar level in the press liquor by addition of theaqueous shards extract. Sucrose inversion is generally carried out byadding invertase in either free or immobilized form to thesugar-enhanced press liquor. Using free enzyme, inversion requires abouta 1-2 hour period at a temperature of about 60° C. and a pH of about4-5, preferably about 4.5. At the end of this period the temperature iselevated (about 80° C.) or the pH raised (to about 7-8) sufficiently toinactivate the enzyme. Following neutralization to pH 7.5, the color ofthe inverted press liquor becomes light brown. There is usually someprecipitatant or flocculant formed following incubation, which appearsto be pectin, cellulose, and hemicellulose.

To avoid cloudiness, the inverted press liquor supernatant should bebriefly heated to boiling or to a temperature within about 25° C. of itsboiling point, e.g. to about 80°-100° C. for about 10-20 minutes. Thisheating produces additional flocculant precipitate containing finelydivided and suspended solids which were not removed during the previousseparation procedures and which may cause cloudiness in thesugar-enhanced press liquor if not removed. It has not yet beendetermined whether such treatment of the filtrate is necessary tosimilarly prevent cloudiness when the shards are separated byultrafiltration, but it appears that this would depend on the details ofthe ultrafiltration process employed.

An immobilized enzyme reactor has also been employed to achieve the samesugar inversion yielding essentially equal amounts of glucose andfructose. An advantage of this system over the free enzyme mode, inaddition to lowered costs for enzymes since the enzyme is re-used over ahalf life of nearly one year, is the significantly faster rate ofinversion (1-2 min. rather than 1-2 hrs.). Another advantage of animmobilized invertase is the energy saved by eliminating the need toinactivate enzymes in the product stream. Since there is no need to heatthe product stream leaving the immobilized invertase reactor, thehemicellulose and pectin in the recombined aqueous phase are removed byheat flocculation and filtration prior to enzymatic inversion in asingle heating step.

Optionally, additional solids from the supernatant press liquor can beremoved at any point by means of extraction with a volatile alcohol,preferably a lower alkanol, e.g. methanol. Approximately equal volumesof methanol and supernatant press liquor are mixed together, whichcauses additional flocculant material to separate. Additionalcentrifugation separates the flocculant solids and gives a furtherclarified supernatant press liquor. Residual alcohol can be removed byevaporation until no odor of alcohol persists in the press liquor, andthe separated flocculant material can be recycled back to the press cakeline. Clarification can also be accomplished by using a series offiltration steps, e.g., using filters, sand, charcoal, and diatomaceousearth.

Filtration through a sand bed, e.g. of 18-30 mesh, is a convenientmethod for removing the flocculated material and other solids which arepresent at this stage. Preferably, the first and last portions of theeffluent are discarded and the column washed with water. The effluentfrom which solids have been removed should be cloudy and have a goldenyellow color.

Activated charcoal may be used to remove solids, proteins, and coloringagents. Here, the charcoal is mixed with the press liquor, and theresulting slurry is vacuum filtered using diatomaceous earth as a filteraid. The filtrate at this stage is clear and light yellow.

If desired, further solids removal can be achieved by microfiltration,e.g. through a Millipore 0.45μ filter. As used herein, the term"microfiltration refers to filtration through a filter having a poresize of 200-100,000 Å which generally filters out components having amolecular weight of less than about 300 kD. The solution should filtereasily and the filtrate be a clear, pale yellow.

Still further clarification and purification of the press liquorfollowing removal of the colloidal layer and solid components can beaccomplished using ion exchange techniques. The inverted press liquor isfirst reacted with a strongly acidic cation exchange resin such as Dowex50WX2 (H⁺ form) to remove cations and various color components from thepress liquor. Other strongly acidic ion exchange resins of suitable meshcan be employed in place of Dowex 50 WX2, e.g. Rohm and Haas IR-116 andIR-118; Ionac C-298; Mitsubishi SK-102 or SK-103; Permutit-Zeocarb 225;and BioRad AG 50W-X2. Following this treatment, the pH of the pressliquor is less than 1, and it should be clear and very pale yellow incolor.

The inverted press liquor is then reacted with a strongly basic anionexchage resin such as BioRad AG1-X8 (Cl⁻ form) to remove anions andadditional color components. Comparable strongly basic anion exchangeresins can be used in place of BioRad AG1-X8, e.g. Dowex 1-X8 (SBR);Rohm and Haas IRA-400; Ionac ASB-1; Mitsubishi SA-100; andPermutit-Zeolit FF. The final solution obtained should be clear,colorless, and odorless, but may have a slightly bitter taste due to theacetic acid of the column.

Alternatively, the clarified and filtered press liquor may be furtherpurified by the use of commercially available electrodialysis equipmentwhich uses a combination of membrane filtration and electrical currentto separate and remove ions from solution leaving the non-ionized sugarsin dilute aqueous solution.

Initial testing of this method indicates that ionic contaminants (salts)are reduced by 50 percent or more in a single pass as measured by theelectrical conductivity of the product stream.

After these procedures are complete, the final concentration of sugarsgenerally ranges from 25-35 mg/ml for fructose and 30-37 mg/ml forglucose. The inverted sugar-enhanced press liquor can be concentrated toa 10 to 15 fold level using a thin film evaporator at moderatetemperatures of about 50° C. to yield a final product which is aviscous, clear and colorless liquid.

The ratio of these sugars in citrus press liquor almost precisely equalstheir ratio in currently marketed "high fructose syrups" which have beenisolated from corn (high fructose corn syrup or HFCS) and certain otheragricultural products, which are sweeteners of commercial importance inthe soft drink and other industries. The concentration of these sugarsfrom citrus press liquor can be easily increased 10-15 fold to that ofhigh fructose syrups by thin film and other evaporation techniques whichdo not require large amounts of energy. The resultant product is anapproximately 50:50 solution of fructose and glucose which isindistinguishable from commercial high fructose syrups having a bulkselling price several fold greater than the animal feed or molasseswhich has previously been prepared from press liquor. Furthermore, thissolution can, by techniques known to those skilled in the art, be easilyand rapidly converted into pure fructose solutions and a precipitate ofgluconic acid salts, having current bulk selling prices approximately anorder of magnitude greater than even HFCS.

While presently preferred as a method for preparing high fructosesyrups, the sugar-enhanced press liquor obtained in accordance with thepresent invention, whether concentrated or not, can be subsequentlytreated in various ways to yield valuable and important products.Examples include but are not limited to additional treatment usingglucose oxidase to oxidize the glucose component to gluconic acid andprecipitate gluconates, yielding pure fructose as described in U.S. Pat.No. 4,345,031, Aug. 17, 1982; use as a feedstock for ethanolfermentation or for the fermentation production of lactic acid andcitric acid, as has been described by Kesterton et al.; use of thesugar-enhanced press liquor in the production of 2,3 butylene glycol byAerobacter, as described by S. K. Long and R. Patrick in AppliedMicrobiology 9: 244-248 (1961); etc.

The colloidal phase of the press liquor can be separated from the pressliquor to yield limonene and other biologically active compounds.Separation of the colloidal phase from the press liquor is preferablycarried out in accordance with the present invention by centrifuging theresidual press liquor subsequent to removal of the shards.

This colloidal layer has been found to contain, inter alia, limonene andmultiple additional citrus oil components, including terpenes. Theresidual liquid phase of the press liquor is composed principally ofsolubilized hemicelluloses, pectins, and fermentable sugars, therebyproviding a starting material for the production of ethanol and otherfermentation products according to known techniques.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The following preferred specific embodiments are,therefore, to be construed as merely illustrative and not limitative ofthe remainder of the disclosure in any way whatsoever. In the followingExamples, the temperatures are set forth uncorrected in degrees Celsius;unless otherwise indicated, all parts and percentages are by weight.

BRIEF DESCRIPTION OF DRAWINGS

The above and other objects, features, and advantages of the presentinention will become more fully apparent to those skilled in the art towhich this invention pertains upon consideration of the presentspecification and annexed drawings, wherein:

FIG. 1 is a flow chart illustrating the processing of citrus pressliquor using free invertase;

FIG. 2 is a similar flow chart using immobilized invertase; and

FIG. 3 is a flow chart illustrating the preparation of gluconate fromcitrus press liquor.

BEST MODE FOR CARRYING OUT THE INVENTION

While the following Examples employed orange press liquor as a startingmaterial, the processes illustrated thereby are equally applicable withappropriate modification as needed to press liquor from other citrusfruit.

EXAMPLE 1 Separation of Suspended Citrus Solids

Referring to the drawings, FIG. 1 gives the general process flowparameters of the presently preferred process. Further details are givenin FIGS. 1 and 2, flow charts for a typical pilot scale operation.Orange peel shards were recovered from a press liquor line using agravity fed microscreen filter at ambient temperature (28° C.) andconveyed to a jacketed mixing tank. The residual press liquor containingthe bright yellow colloidal layer (which represented about 2-3 percentof the liquid phase by volume) was collected from the filter and pumpedinto a continuous feed centrifugal separator. Three components wererecovered: a lower density, bright yellow colloid; a higher densityaqueous phase containing essentially the sugar values of the pressliquor; and a solid "shards" pellet containing peel, pulp and seedresidues.

The separated shards were conveyed first to a stirred reactor where theywere heated in water for 10-20 minutes at 65°-85° C. to extractadditional amounts of sugars. The shards were then screen filtered asbefore, and the water extract added to the press liquor in the stirredreactors. Remaining shards were conveyed to the feed mill to add weightand substance to dried citrus pulp products.

EXAMPLE 2 Sucrose Inversion with Free Invertase

Press juices and the sugar-containing water extract from the shardmixing tank were pumped into a jacketed and temperature-controlledstirred reactor. Yeast invertase granules were then added to the reactorand the sucrose inversion reaction allowed to proceed at 60° C. forapproximately 2 hours at controlled pH. At the end of the 2-hourreaction period, tank temperature was elevated to 85° C. forapproximately 15 minutes to inactivate the enzyme and to precipitatesoluble pectin and cellulose.

As shown in Table 1, there is little or nothing to be gained by addinginvertase to the press liquors at any other step in the process.Adequate inversion was achieved by simply adding the invertase to thestirred reactors.

                  TABLE 1                                                         ______________________________________                                        Procedure           Percent Sucrose                                           (2 hours at 60° C.)                                                                        Inverted Remaining                                        ______________________________________                                        No invertase added   0       100                                              Invertase added directly to press                                                                 100       0                                               juice                                                                         Invertase added before heating                                                                    100       0                                               Invertase added after heating but                                                                 100       0                                               before mixed bed clarifying filter                                            ______________________________________                                    

EXAMPLE 3 Sucrose Inversion with Immobilized Invertase

Invertase enzyme, commercially available from Miles Laboratories, wasslurried in distilled water and centrifuged to remove insolubles. Astack of microporous plastic sheets produced by Amerace Corp. wasprepared to receive the enzyme by sequential flushing withpolyethyleneimine in saline solution and gluteraldehyde. Thegluteraldehyde, now bound to the microporous plastic sheet was reactedwith the amine groups of the invertase enzyme again by recirculation ofthe enzyme solution through the sheets.

Following invertase immobilization, the sucrose-rich aqueous processstream is first filtered to remove insolubles which might plug thereactor, and then pumped through the immobilized invertase reactor. Forthe purpose of this example, the sucrose level was adjusted to 5 percent(wt/wt) and a sample was analyzed by liquid chromatography to confirmthe concentration. The system was operated at constant flow rate, buttwo temperatures were tested in order to compare efficiencies. The tablebelow contains the results of our LC analysis of the time experimentalruns:

                  TABLE 2                                                         ______________________________________                                        Immobilized Invertase                                                                    Percent of Total Sugars                                                       Sucrose  Glucose  Fructose                                         ______________________________________                                        Feedstock    96.9        1.2      1.8                                         Reaction at 20° C.                                                                  24.2       41.5     34.3                                         Reaction at 45° C.                                                                  11.7       47.3     41.0                                         ______________________________________                                    

EXAMPLE 4 Purification

The inverted glucose and fructose solution from Example 2 was pumped toa mixed bed clarifying filter containing industrial grade filtrationsand, activated charcoal, and diatomaceous earth layers in order topartially deodorize and decolorize the resulting glucose and fructosesolution and to remove soluble contaminants and insoluble pectin andcellulose fines before passage through (first to Dowex-50 then toDowex-1) deionizing columns. A water wash of this mixed bed clarifyingfilter was undertaken at the end of each reaction period and the washreturned to press cake line leading to the dried citrus pulp feed mill.The effluent leaving the deionizing columns was a clear, colorless, andodorless solution containing approximately 10-15 grams of sugars per 100ml. More than 95 percent of the sugar content was glucose and fructose.This solution was concentrated 10 to 15 fold to a solids level of 90-95percent using a Rotovap thin film evaporator at 50° C. to give a clean,colorless, viscous product containing about 44 percent fructose and 48percent glucose. The overall yield of the process in terms of solids wasin excess of 95 percent, i.e. over 95 percent of the inverted glucoseand fructose was recovered from the effluent emerging from thedeionizing columns.

EXAMPLE 5 Gas Chromotography

Differences between the various materials involved in the process werestudied and illustrated by gas chromatography. Four sugar "peaks" weredemonstrated for both clarified citrus press liquor and for the hotwater extract of citrus shards. These include the α- and β-anomers ofglucose, the α- and β-anomers of fructose, a sucrose peak, an unknownpeak which behaves like mannoheptulose, and a maltose peak, the latterbeing an internal standard used for analytical purposes only.

The only difference from the reference sugar feedstock was the completeabsence of a sucrose peak in the process material which demonstrated thepresence only of the α- and β-anomers of fructose, the α- and β-anomersof glucose, and a sugar which behaves chromatographically likemannoheptulose.

EXAMPLE 6 Comparison With High Fructose Corn Syrup

The chromatographs and chemical proportions of fructose and glucose inthe process material were compared with commercial preparations of HighFructose Corn Syrup (HFCS). The only difference between the referencematerial and the process material was the absence of the presumedmannoheptulose sugar in the reference preparations. The proportions ofsugars and the process material and the reference material werevirtually identical, as illustrated in Table 3:

                  TABLE 3                                                         ______________________________________                                        Proportion of Sugars in HFCS and Process Material                                                    Percent                                                Material   Fructose    Glucose  Other Sugars                                  ______________________________________                                        Isomerose ™ 100                                                                       43          56       6                                             Isomerose ™ 500                                                                       55          41       4                                             Process Material                                                                         47          49       ˜4                                      ______________________________________                                    

EXAMPLE 7 Chemical Analysis

Further chemical analysis was conducted on the process material afterinversion according to Example 2. Some protein material occasionallyremained in an order of magnitude comarable to that usually encounteredin the commercial HFCS preparations. This appears to be a function of pHand of the effectiveness of the mixed bed clarifying filter in removingresidual amounts of invertase protein.

Depending upon the extent of evaporation, the solids content afterinversion can be made to vary from 50-95 percent solids, andcorrespondingly 5-50 percent moisture content, as desired. The dry basiscomposition was 99+ percent carbohydrate with an ash content of lessthan 0.05 percent. The process material was almost entirelyindistinguishable from high fructose syrups of corn or otheragricultural origin. The only detected difference was the presence ofthe unknown sugar (presumably mannoheptulose), comparable to the "othersaccharides" component found in commercial Isomerose and other highfructose syrup preparations.

EXAMPLE 8 Growth Inhibition by Colloidal Layer

Equal volumes (100 ml each) of raw citrus press liquor were centrifugedat 6000 rpm to give three distinct layers previously described. Thecolloidal layer of one batch was removed by skimming and filteringthrough cheesecloth and the middle aqueous phase decanted from the shardpellet. The colloidal layer of a control batch was not removed, butdecanted along with the aqueous phase from the shards. These aqueousphases with and without the colloidal phase were diluted 1:1 with water,sterilized by autoclaving, and compared for their ability to support thegrowth of Saccharomyces cerevisiae (ATCC 4126). The aqueous phase withthe colloidal layer did not support growth of the yeast, and viablecounts of the organisms dropped upon incubation. The aqueous phasewithout the colloidal layer supported growth of the yeast to allowdirect ethanol fermentation.

Similar experiments demonstrated that a component in the colloidal layerinhibited the growth of Clostridium thermohydrosulfuricum (ATCC 33,223)used to convert sugar to alcohol, and of Clostriduim thermocellum (ATCC27,405) used to break down cellulose into sugars and of Gluconobacteroxydans subs. suboxydans (ATCC 621). However, antibacterial activity ofthe colloidal layer was selective as evidenced by the fact that it didnot similarly inhibit Lactobacillus bulgaricus (ATCC 11,842),Lactobacillus casei, subp. rhamnosus (ATCC 7,469), or Lactobacilluslactis (ATCC 12,315). It appears that this selective inhibition is dueto the presence of limonene and/or terpenes in the colloidal layer,which became gummy when dried.

EXAMPLE 9 Fermentation

Citrus press liquor without the colloidal layer was prepared asdescribed in Example 8 and successfully used as a feedstock for anethanol fermentation using Saccharomyces cerevisiae (ATCC 4126). Thefermentation was complete after a 36 hour incubation at 30° C.

EXAMPLE 10 Recovery of Citrus Terpenes

The bright yellow colloidal material recovered from the citrus pressliquor during the continuous separation of Example 1 was distilled undervacuum and mild heat (60° C.) and the distillate was recovered from thevapor phase using a water cooled condensor operating at 18° C. Thisdistillate was a colorless liquid having a distinct citrus aroma and wasshown by mass spectral analysis to be predominantly limonene, useful asa perfume and fragrance.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those specifically used inthe examples. From the foregoing description, one skilled in the art towhich this invention pertains can easily ascertain the essentialcharacteristics thereof and, without departing from the spirit and scopeof the present invention, can make various changes and modifications toadapt it to various usages and conditions.

Industrial Applicability

The process described herein greatly increases the economic value ofcitrus press liquors which have heretofore been used as a source ofcitrus molasses and dry citrus pulp animal feed of low economic value.Furthermore, by removing fermentation inhibitation components in thecolloidal layer of press liquor, citrus sugars obtained therefrom cannow be used as a fermentation feedstock.

What is claimed is:
 1. A process for recovering a plurality of usefulproducts from a citrus press liquor line from which a citrus press cakeand screenable solids have been removed, which process comprises:(A)ultrafiltering the screen filtered press liquor to form (i) a permeatefraction consisting essentially of limonene-containing biocidally activematerials and an aqueous solution of the dissolved sugars and solublepolymeric carbohydrates from said press liquor, and (ii) a retentatefraction consisting essentially of solid citrus fragments and shardsfrom said press liquor; (B) recovering the biocidally active materialsfrom the permeate fraction to form an aqueous phase which issubstantially free of said biocidally active materials and consistsessentially of the dissolved sugars and soluble polymeric carbohydratesfrom said press liquor; (C) extracting fructose, glucose, and sucrose bysuspending the retentate fraction from step (A) in a volume of water at65-85 degrees C. roughly corresponding to the original volume of saidpress liquor for about 10 to 15 minutes; (D) separating the residualwater-insoluble material remaining after the aqueous extraction of step(C) and combining it with a press cake from which citrus press liquorhas been separated to increase the solids content thereof by at least 10percent on a dry weight basis; and (E) combining the separated aqueousextract from step (C) with the aqueous phase from step (B) to increasethe hexose content of said aqueous phase by at least 20 percent byvolume.
 2. A process according to claim 1, wherein the fructose,glucose, and sucrose equivalent of the citrus press liquor is increasedto a concentration comparable to that of high fructose corn syrup.
 3. Aprocess according to claim 2, further comprising inverting the extractedsucrose from step (C) to form substantially equimolar amounts of glucoseand fructose.
 4. A process according to claim 3, wherein the citruspress liquor is treated with invertase following recombination with theaqueous extract from step (E).
 5. A process according to claim 1,wherein the water-insoluble material from step (D) is further convertedinto dried citrus pulp.
 6. A process according to claim 1, furthercomprising fermenting at least one sugar extracted in step (C).
 7. Aprocess according to claim 3, further comprising converting at least oneof said sugars into a corresponding carboxylic acid or salt thereof. 8.A process according to claim 7, wherein glucose is converted intogluconic acid or a salt thereof, further comprising recovering fructosefrom the resultant solution.
 9. A process according to claim 3, furthercomprising heating the inverted press liquor to about 80-100 degrees C.to form a flocculent precipitate and separating the precipitate from theinverted press liquor to prevent cloudiness therein.
 10. A processaccording to claim 9, wherein the separated flocculent is combined witha press cake from which citrus press liquor has been separated.
 11. Aprocess according to claim 3, further comprising removing additionalsolids from the sugar-enhanced press liquor from step (C) by alcoholextraction after the separating of step (D).
 12. A process according toclaim 3, further comprising clarifying the inverted press liquor bysequential reaction with a strongly acidic, then a strongly basic, ionexchange resin.